More mystery wires....

[SiberianDVM]

'77 911S Targa.

I have the following mystery wires that I could use some help determining their purpose:

Large (12ga?) red with longitudinal green stripe below front fuse box.


Medium (18ga?) green with longitudinal yellow also below front fuse box, terminating in a pair of male spade lugs.


Small (22ga?) black with transverse purple terminating in small brass lug, also below fuse box


Thanks in advance

[rwest]

Do you have an aftermarket stereo or alarm?

The top set of wires don't appear to be factory, the black purple one does.

I'll go to the garage in a little bit and see if I can locate it on my car.

[rwest]

The black box with fat red wire going into it is not on my car, does it maybe have something to do with the other heavy gauge wires?

I couldn't find the black purple wire near my fuse box.

[SiberianDVM]

Originally Posted by rwest

The black box with fat red wire going into it is not on my car, does it maybe have something to do with the other heavy gauge wires?

I couldn't find the black purple wire near my fuse box.

That is a 2 ga battery wire connector/MEGA fuse box that I just installed as part of the battery relocate and kill switch.

No aftermarket alarm now; some PO had installed one previously but I thought we got rid of all of it.

Yes, on the aftermarket stereo, but I just did that one, and I utilized the factory wiring, with the exception of one new power lead.

[rwest]

I'm no expert on wiring, but if I'm reading the wiring diagram correctly, black purple appears to be used for the power mirror switch and the tach. Do both of these work?

[SiberianDVM]

Tach works, although it is not original. The car came to me (owner #5) with a 3.0 carbed motor, so I had a shop install my 3.2 Motronics motor from my totaled '84. They had to replace the tach to make it compatible. I think they spliced a red wire to a different black/purple wire to go to the tach. If I can find some similar black/purple wire I will try to make it look more authentic.

Some time in the past, somebody replaced the power mirrors with Aero mirrors. This probably is the one that is loose. Many thanks.

I have been trying to find a decent wiring diagram for a '77, but these cars seem to be orphans. All the wiring diagrams I have found have been illegible or too small to make anything out.

[rwest]

I got a download from Bob Kontack that seems to be pretty good diagram.
1977 Wiring diagram-Will e-mail fo' free


There is a guy on here who makes custom wiring harnesses- maybe timmy2? I believe he has all the different wires and will sell you a length.

Found it Building SC and Mid Year Engine Harnesses

[SiberianDVM]

Many thanks. I will download and print these out ASAP.

[timmy2]

https://www.dropbox.com/sh/03bgz8h8ot93m9c/AACPJ3BqUcIPNCrdpgPYNA0ea?dl=0
All the schematics you might need.

[SiberianDVM]

Gracias. Still can't find those darn red/green and green/yellow wires........

[rwest]

Originally Posted by SiberianDVM

Gracias. Still can't find those darn red/green and green/yellow wires........

Got to be aftermarket, can you track them down? If alarm, maybe they go to starter area or possibly to doors for aftermarket power locks? Check the area where the alarm brain was installed and see if they end there.

[timmy2]

A/C installed?
Hard to find really good schematics for the early systems.
The supplementals in the link I provided may help.

[SiberianDVM]

I will try to track them down. Unfortunately, working max overtime due to holiday coming up, so it probably won't be until this weekend.

[SiberianDVM]

Originally Posted by timmy2

A/c ?

Possibility. Car had dealer installed a/c when sold new, and POs let it go to crap, so we ripped it out when installing the new engine.

[timmy2]

I just edited my post you quoted.

[E Sully]

Your green, green/yellow are probably A/C wiring.
A few more details on your car would help. It started as a 77S, had a 3.0 SC engine with carbs swap, then a 3.2 engine installed.
What ignition and distributor is the car using now? Is the 3.2 using Motronic, or carbs? When you had them put in the 3.2, did they use any of the Motronic wiring harness?
The Large red/green wire looks like it would be a fuel pump wire.

[SiberianDVM]

Originally Posted by E Sully

Your green, green/yellow are probably A/C wiring.
A few more details on your car would help. It started as a 77S, had a 3.0 SC engine with carbs swap, then a 3.2 engine installed.
What ignition and distributor is the car using now? Is the 3.2 using Motronic, or carbs? When you had them put in the 3.2, did they use any of the Motronic wiring harness?
The Large red/green wire looks like it would be a fuel pump wire.

Car is using the entire Motronics system from the donor car.

Looking at the schematics for the A/C system (separate pages from main car schematics) it looks like they may be A/C wires, but still not sure. I will try to back trace them.

[E Sully]

Then the green/red is the power for the fuel pump from the DME relay. It would have gone to a 25 amp fuse, and then to the fuel pump in the '84. If your car is using the original '77 fuel pump wiring, I would cap it off, as it has battery voltage on it. Another option is to use the Motronic green/red to feed the fuel pump as it kills the fuel pump for safety reasons if the engine stops.
The other 2 are A/C.
Here's a sketch I made years back when I put a 3.2 in my '73.

[SiberianDVM]

Originally Posted by E Sully

Then the green/red is the power for the fuel pump from the DME relay. It would have gone to a 25 amp fuse, and then to the fuel pump in the '84. If your car is using the original '77 fuel pump wiring, I would cap it off, as it has battery voltage on it. Another option is to use the Motronic green/red to feed the fuel pump as it kills the fuel pump for safety reasons if the engine stops.
The other 2 are A/C.
Here's a sketch I made years back when I put a 3.2 in my '73.

Aha! Very instructive. I didn't realize that all those wires were in one giant bundle. I will cap it off for now, but eventually I would like to use the Motronic wire to feed the fuel pump, but I'm not sure that I can do it without buggering it up.

[fred cook]

I pulled one of my old wiring schematics and found the following:

The red/green wire runs from bottom of last fuse (21) to the fuel pump relay. Check to see if it has power on it. I think it gets it's power from the fuse block.
The green/yellow should run from the bottom of fuse #11 (3rd fuse in second block) to the backup lamp switch.

could not find anything on the black/purple wire at the fuse box. Probably not connected there.

Hope this helps.